Refractory composition



Patented Feb. 21, 1950 REFRACTORY COMPOSITION John M. Mochel, Corning,N. Y., assignor to Corning Glass Works, Corning, N. Y., a corporation ofNew York No Drawing. Application November 6, 1947, Serial No. 184,525

7 Claims.

This invention relates to refractory compositions and bodies and has forits primary object to provide bodies of great refractoriness having highdensity and superior resistance to corrosion and erosion by flowingmolten glass.

Another object is to provide a refractory body of chromic oxide which issuitable for use in contact with flowing molten glass withoutobjectionably coloring the glass.

Another object is to mold and fire chromic oxide so as to promotemaximum shrinkage and bring it to the greatest possible density.

Another object is to render it non-conducting of electricity.

Chromic oxide, Cr203, is very refractory and many compositions have beenproposed which contain it in various proportions, usually in the form ofchromite ore. Such refractory compositions have not been employed forglass contacting refractories because they are too porous or too poorlybonded, as a result of which they are eroded b the molten glass andcause objectionable discoloration thereof. In some instances suchdiscoloration, if reduced to a minimum, would not be objectionable.However, prior compositions containing chromic oxide have not beensuitable for various reasons. They are not sufficiently dense to besatisfactorily resistant to corrosion and erosion by the molten glass.Moreover, chromic oxide is a semi-conductor of electricity when heatedat elevated temperatures and this is objectionable in a refractory bodywhich it is desired to use in connection with the electrical melting ofglass without it being a part of the electrical circuit.

I have now discovered that these difficultiesare overcome and theforegoing objects may be 2v attained by using a composition which,exclusive of impurities, consists of CrzOs, T102, and an alkalineearthmetal oxide (R0), the Cr2O3 being at least the TiOz being from about 1%to about 15% and the ratio TiOz/RO being from about .5/1 to about 5/1.

I have found that when TiOz and an alkaline earth metal oxide, MgO,Ca'O, SrO or BaO, in proper proportions are introduced into a refractorybody composed of C1'203, they act jointly as a mineralizing or shrinkingagent for the CrzOs and also cause a very decided increase in theelectrical resistivity of the body. Although the composition may contain80% CrzOs, it preferably should contain at least 90% C12O3, theremainder being TiOz and alkaline earth oxide exclusive of impurities.Neither the alkaline earth oxide nor TiOz is effective when used alone.Maximum effeet is produced by 8% TiOz and 2% CaO, or

4% T102 and 2% $10, or 2% TiOz and 2% BaO,'

but other amounts and ratios are also effective to some extent at least,as will appear.

For best results I have found it desirable to employ a relatively pureand finely powdered CrzOs. The composition is mixed and molded in theusual manner by slip casting or pressing. Since the alkaline earth metaloxides are slightly soluble in Water, they should be introduced into thebatch as the carbonates. After being molded the body is dried and firedat temperatures up to 1550 C. and above.

Without limiting the invention thereto the following compositions inpercent by weight were fired at a maximum temperature of 1550 C. andshow the change in density and percentage of voids which is caused bythe addition of T102 and an alkaline earth metal oxide to C12O3.

. Apparent Percent Ratio No. 01203 T102 CaO SrO BaO Density Voids Tim/R01 12 4. 38 13 4 1 8 4. 51 12 4J1 4 4.14 16 4/1 5 2 3. 82 26 4/1 .75 1 3.63 29 4/1 2 3. 84 36 1/1 4 3. 63 30 4/1 4 3.89 25 2/1 4 3. 81 27 1. 5/12 3. 28 37 5/1 2 3. 41 34 3/1 2 3. 68 29 1. 6/1 2 4.0 23 Ill 2 3. 95 2466/1 3. 13 40 Composition 15 shows for comparison the apparent densityand percentage of voids which characterize a body composed of CI203alone. Composition 2 contains the optimum amounts and ratio of T102 andCaO; composition 8 contains the optimum amounts and ratio of T102 andSrO; composition 13 contains the optimum amounts and ratio of T102 andBaO.

A small bar of composition 2 was tested by partly immersing'it for threedays in molten glass of a composition commonly used. Its resistance tocorrosion was far superior to that of the refractories previously usedWith that glass. The electrical resistivity of these compositions isvery high, even at elevated temperatures.

I claim:

1. A refractory composition which, exclusive of impurities, consists ofCrzOs, TiO2 and an alkaline earth metal oxide (R) selected from theclass consisting of MgO, CaO, SrO and B20, the CIzOs being at least 80%,the T102 being from about 1% to about 15% and the ratio TiO2/RO beingfrom about .5/1 to about'5/ 1.

2. A refractory composition which, exclusive of impurities, consists ofCrzOs, T102 and CaO, the CrzOa being at least 80%, the T102 bein fromabout 1% to about 15% and the ratio TiOz/CaO being from about .5/1 toabout 5/1.

4 impurities, consists of approximately 90% CrzOs, 8% T102 and 2% C210.

4. A refractory composition which, exclusive of impurities, consists ofCr2O3, T102 and SrO', the CrzOs being at least the T102 being from about1% to about 15% and the ratio TiOz/SrO being from about .5/1 to about5/ 1. a

5. A refractory composition which, exclusive of impurities, consists ofapproximately 94% CrzOs, 4% T102 and 2% SrO. v

6. A refractory composition which, exclusive of impurities, consists ofCr2O3, T102 and 32.0, the C1203 being at least 80%, the T102 being fromabout 1% to about 15% and the ratio TiOz/BaO being from about .5/1 toabout 5/ 1.

v 7. A refractory composition which, exclusive of impurities, consistsapproximately of 96% CrzOs,

2% T102 and 2% BaO.

JOHN M. MOCHEL.

REFERENCES CITED I UNITED STATES PATENTS Number .Name Date 2,271,362Field Jan, 2'7, 1942 2,271,364 Field Jan. 27, 1942

1. A REFRACTORY COMPOSITION WHICH, EXCLUSIVE OF IMPURITIES, CONSISTS OFCR2O3, TIO2 AND ANA ALKALINE EARTH METAL OXIDE (RO) SELECTED FROM THECLASS CONSISTED OF MGO, CAO, SRO, AND BAO, THE CR2O3 BEING AT LEAST 80%,THE TIO2 BEING FROM ABOUT 1% TO ABOUT 15% AND THE RATIO TIO2/RO BEINGFROM ABOUT .5/1 TO ABOUT 5/1. METAL ION OF AT LEAST ONE ELEMENT SELECTEDFROM THE GROUP CONSISTING OF CALCIUM, ZINC, COBALT, MAGNESIUM, CADMIUM,IRON, ALUMINUM, BARIUM, STRONTIUM, MANGANESE, CHROMIUM, AND NICKEL, ATLEAST 200 P. P. M. BY WEIGHT OF A WATER-SOLUBLE ALKALI-METAL PHSPHATEGLASS AND AT LEAST 10 P. P. M. OF AN OXIDIZING AGENT SELECTED FROM THEGROUP CONSISTING OF WATER-SOLUBLE INORGANIC NITRATES, NITRITES,SULFITES, PERMANGANATES, CHROMATES, FERRICYANIDES, DICHROMATES, ANDPERBORATES, AND MAINTAINING THE RATIO OF THE PHOSPHATE GLASSCONCENTRATION IN SAID SOLUTION TO THE CONCENTRATION OF THE METAL IONTHEREIN BETWEEN THE VALUES OF ABOUT 0.05:1 AND ABOUT 12:1.